Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

ABSTRACT

A variable magnification optical system includes, in order from an object side, a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power; upon zooming from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group and a distance between the second lens group and the third lens group being varied. The variable magnification optical system further includes a V lens group GV having negative refractive power and being moved to have a component in a direction perpendicular to the optical axis, and an F lens group GF having positive refractive power and being moved along the optical axis upon focusing from an infinitely distant object to a close object, the V lens group GV being disposed on the more object side than the F lens group GF. Thereby, it is possible to provide the compact variable magnification optical system with a high zoom ratio and high performance, an optical apparatus therewith and a method for manufacturing the variable magnification optical system.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical apparatus therewith and a method for manufacturingthe variable magnification optical system.

BACKGROUND ART

Conventionally, there has been proposed many a variable magnificationoptical system whose most object side lens group has positive refractivepower suitable for an interchangeable lens for a camera, a digitalcamera, a video camera or the like. For example, refer to JapanesePatent Application Laid-Open No. 2011-232543.

PRIOR ART REFERENCE DOCUMENT Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2011-232543

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the conventional variable magnification optical systems,while maintaining a high zoom ratio, when aiming at downsizing of thezoom optical systems, it is difficult to achieve sufficiently highoptical performance.

The present invention is made in view of the above-described problem,and has an object to provide a compact variable magnification opticalsystem with a high zoom ratio and high optical performance, an opticalapparatus therewith, a method for manufacturing the variablemagnification optical system.

Means for Solving the Problem

In order to solve the above-mentioned problem, according to a firstaspect of the present invention there is provided a variablemagnification optical system comprising, in order from an object side: afirst lens group having positive refractive power; a second lens grouphaving negative refractive power; and a third lens group having positiverefractive power;

upon zooming from a wide-angle end state to a telephoto end state, adistance between the first lens group and the second lens group beingvaried, and a distance between the second lens group and the third lensgroup being varied;

a V lens group having negative refractive power and being moved so as tohave a component in a direction perpendicular to the optical axis, andan F lens group having positive refractive power and being moved alongthe optical axis upon focusing from an infinitely distant object to aclose object being disposed; and

the V lens group being disposed on a more object side than the F lensgroup.

According to a second aspect of the present invention, there is providedan optical apparatus equipped with the variable magnification opticalsystem according to the first aspect of the present invention.

According to a third aspect of the present invention, there is provideda variable magnification optical system comprising, in order from anobject side: a first lens group having positive refractive power; asecond lens group having negative refractive power; and a third lensgroup having positive refractive power;

upon zooming from a wide-angle end state to a telephoto end state, adistance between the first lens group and the second lens group beingvaried, and a distance between the second lens group and the third lensgroup being varied; and

the third lens group including an F lens group having positiverefractive power and being moved along the optical axis upon focusingfrom an infinitely distant object to a close object.

According to a fourth aspect of the present invention, there is providedan optical apparatus equipped with the variable magnification opticalsystem according the third aspect of the present invention.

According to a fifth aspect of the present invention, there is provideda variable magnification optical system comprising, in order from anobject side: a first lens group having positive refractive power; asecond lens group having negative refractive power; a third lens grouphaving positive refractive power; a fourth lens group having negativerefractive power; and a fifth lens group having positive refractivepower;

upon zooming from a wide-angle end state to a telephoto end state, adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, adistance between the third lens group and the fourth lens group, and adistance between the fourth lens group and the fifth lens group beingvaried, the first lens group being moved along the optical axis, theposition of the fifth lens group being fixed; and

the following conditional expression being satisfied:0.170<(−f4)/f5<0.400where f4 denotes a focal length of the fourth lens group, and f5 denotesa focal length of the fifth lens group.

According to a sixth aspect of the present invention, there is providedan optical apparatus equipped with the variable magnification opticalsystem according to the fifth aspect of the present invention.

According to a seventh aspect of the present invention, there isprovided a method for manufacturing a variable magnification opticalsystem comprising: in order from an object side, a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; and a third lens group having positive refractivepower; the method comprising the steps of:

disposing a V lens group having negative refractive power which is movedso as to have a component in a direction perpendicular to the opticalaxis, and an F lens group having positive refractive power which ismoved along the optical axis upon focusing from an infinitely distantobject to a close object;

disposing the V lens group on a more object side than the F lens group;and

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group, and a distance between the second lens group and thethird lens group are varied.

According to an eighth aspect of the present invention, there isprovided a method for manufacturing a variable magnification opticalsystem comprising: in order from an object side, a first lens grouphaving positive refractive power; a second lens group having negativerefractive power; and a third lens group having positive refractivepower; the method comprising the steps of:

constructing the third lens group to include an F lens group havingpositive refractive power which is moved along the optical axis uponfocusing from an infinitely distant object to a close object; and

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group, and a distance between the second lens group and thethird lens group are varied.

According to a ninth aspect of the present invention, there is provideda method for manufacturing a variable magnification optical systemcomprising: in order from an object side, a first lens group havingpositive refractive power; a second lens group having negativerefractive power; a third lens group having positive refractive power; afourth lens group having negative refractive power; and a fifth lensgroup having positive refractive power; the method comprising the stepsof:

constructing the fourth lens group and fifth lens group to satisfy thefollowing conditional expression:0.170<(−f4)/f5<0.400where f4 denotes a focal length of the fourth lens group, and f5 denotesa focal length of the fifth lens group; and

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group, a distance between the second lens group and thethird lens group, a distance between the third lens group and the fourthlens group and a distance between the fourth lens group and the fifthlens group are varied, the first lens group is moved along the opticalaxis, and the position of the fifth lens group is fixed.

Effect of the Invention

According to the first, second and seventh aspects of the presentinvention, it is possible to provide the variable magnification opticalsystem, the optical apparatus therewith and the method for manufacturingthe variable magnification optical system in which a high zoom ratio,downsizing and high optical performance can be achieved. Also, highoptical performance can be achieved upon focusing and even when the lensgroup is moved so as to have a component in the direction perpendicularto the optical axis.

According to the third, fourth and eighth aspects of the presentinvention, it is possible to provide the variable magnification opticalsystem, the optical apparatus therewith and the method for manufacturingthe variable magnification optical system by which a high zoom ratio,downsizing and high optical performance can be achieved, and highoptical performance can be obtained even upon focusing.

According to the fifth, sixth and ninth aspect of the present invention,it is possible to provide the variable magnification optical system, theoptical apparatus and the method for manufacturing the variablemagnification optical system by which a high zoom ratio, downsizing andhigh optical performance can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are sectional views showing a wide-angle end state,an intermediate focal length state and a telephoto end state of avariable magnification optical system according to a first example whichis common to the first to third embodiments of the present application.

FIGS. 2A, 2B and 2C are graphs showing various aberrations upon focusingon an infinitely distant object in the wide-angle end state, in theintermediate focal length state and in the telephoto end state of thevariable magnification optical system according to the first example ofthe present application.

FIGS. 3A, 3B and 3C are graphs showing various aberrations upon focusing(shooting magnification—0.01 times) on the close object in thewide-angle end state, in the intermediate focal length state and in thetelephoto end state of the variable magnification optical systemaccording to the first example of the present application.

FIGS. 4A, 4B and 4C are graphs showing meridional transverse aberrationsat the time of conducting vibration reduction upon focusing on theinfinitely distant object in the wide-angle end state, in theintermediate focal length state and in the telephoto end state of thevariable magnification optical system according to the first example ofthe present application.

FIGS. 5A, 5B and 5C are sectional views showing a wide-angle end state,an intermediate focal length state and a telephoto end state of avariable magnification optical system according to a second examplewhich is common to the first to third embodiments of the presentapplication.

FIGS. 6A, 6B and 6C are graphs showing various aberrations upon focusingon an infinitely distant object in the wide-angle end state, in theintermediate focal length state and in the telephoto end state of thevariable magnification optical system according to the second example ofthe present application.

FIGS. 7A, 7B 7C are graphs showing various aberrations upon focusing ona close object (shooting magnification—0.01 times) in the wide-angle endstate, in the intermediate focal length and in the telephoto end stateof the variable magnification optical system according to the secondexample of the present application.

FIGS. 8A, 8B and 8C are graphs showing meridional transverse aberrationsat the time of conducting vibration reduction upon focusing on theinfinitely distant object in the wide-angle end state, in theintermediate focal length state and in the telephoto end state of thevariable magnification optical system according to the second example ofthe present application.

FIG. 9 is a diagram showing a camera equipped with the variablemagnification optical system according to the first to third embodimentsof the present application.

FIG. 10 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the firstembodiment of the present application.

FIG. 11 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the secondembodiment of the present application.

FIG. 12 is a flowchart schematically showing a method for manufacturingthe variable magnification optical system according to the thirdembodiment of the present application.

EMBODIMENTS FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, a variable magnification optical system according to afirst embodiment of the present application, an optical apparatustherewith and a method for manufacturing the variable magnificationoptical system will be explained.

The variable magnification optical system according to the firstembodiment of the present application comprises: in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; and a third lens group havingpositive refractive power; upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group being varied, and a distance between the second lensgroup and the third lens group being varied. With this construction, inthe variable magnification optical system according to the firstembodiment of the present application, it is possible to realize zoomingfrom the wide-angle end state to the telephoto end state and suppressrespective variations of distortion, astigmatism and sphericalaberration caused by zooming.

The variable magnification optical system according to the firstembodiment of the present application includes a V lens group havingnegative refractive power which is moved so as to have a component in adirection perpendicular to the optical axis, and an F lens group havingpositive refractive power which is moved along the optical axis uponfocusing from an infinitely distant object to a close object. In thevariable magnification optical system according to the first embodimentof the present application, with the V lens group being moved so as tohave a component in the direction perpendicular to the optical axis, itis possible to move an image and correct an image blur due to a camerashake, in other words, carry out vibration reduction. Also, with theabove-mentioned construction, in the state that the V lens group ismoved in the direction perpendicular to the optical axis, that is, inthe state that the V lens group is decentered, it is possible tosuppress decentering coma generated in the V lens group. Also, it ispossible to suppress variation of spherical aberration and variation ofastigmatism generated in each lens group upon zooming.

In the variable magnification optical system according to the firstembodiment of the present application, the V lens group is disposed onthe more object side than the F lens group. With this construction, theratio of a moving amount of an image to a moving amount of the V lensgroup can be made larger in the telephoto end state than in thewide-angle end state. Accordingly, it is possible to suppress the movingamount of the V lens group to be needed in the telephoto end state, andsuppress decentering coma generated in the V lens group. Also, with theF lens group being disposed on the more image side than the V lensgroup, it is possible to suppress variation of the focal length of thevariable magnification optical system according to the first embodimentof the present application upon focusing thereby enabling to suppressvariation in angle of view in association with focusing and achieve highoptical performance.

With the above construction, it is possible to realize the compactvariable magnification optical system with a high zoom ratio and highoptical performance. High optical performance can be achieved uponfocusing and even when the lens group is moved so as to have a componentin the direction perpendicular to the optical axis.

Also, the variable magnification optical system according to the firstembodiment of the present application preferably satisfies the followingconditional expression (1):0.240<ff/(−fv)<4.000  (1)where ff denotes a focal length of the F lens group, and fv denotes afocal length of the V lens group.

The conditional expression (1) defines the range of the proper focallength ratio of the F lens group and the V lens group. With the variablemagnification optical system according to the first embodiment of thepresent application satisfying the conditional expression (1), it ispossible to suppress decentering coma at the time when vibrationreduction is carried out by moving the V lens group so as to have thecomponent in the direction perpendicular to the optical axis. Further,it is possible to suppress variation of spherical aberration andvariation of astigmatism to be generated in each lens group uponfocusing.

When the value of ff/(−fv) in the conditional expression (1) accordingto the variable magnification optical system according to the firstembodiment of the present application is equal to or falls down thelower limit value, variation of spherical aberration and variation ofastigmatism generated in each lens group upon focusing become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (1) to 0.490. Further, in order to secure the effect of thepresent application more surely, it is preferable to set the lower limitvalue of the conditional expression (1) to 0.630.

On the other hand, when the value of ff/(−fv) in the conditionalexpression (1) of the variable magnification optical system according tothe first embodiment of the present application is equal to or exceedsthe upper limit value, decentering coma upon conducting vibrationreduction becomes large. Also, the moving amount of the F lens groupupon focusing becomes large. Therefore, upon focusing, the state oflight passing through the F lens group is largely changed, it becomesimpossible to suppress variation of spherical aberration and variationof astigmatism generated in the F lens group. Incidentally, in order tosecure the effect of the present application surely, it is preferable toset the upper limit value of the conditional expression (1) to 2.800.Further, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (1) to 1.800.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, upon zooming from thewide-angle end state to the telephoto end state, it is desirable thatthe distance between the V lens group and the F lens group in thedirection of the optical axis is made unchangeable. With thisconstruction, the V lens group and F lens group can be disposed in asame lens group, and it is possible to easily suppress mutual tiltdecentering of the V lens group and F lens group generated at the timeof manufacture. Accordingly, it is possible to suppress decentering comaand astigmatism generated due to tilt decentering of the V lens groupand F lens group.

Also, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that afourth lens group having negative refractive power is disposed on theimage side of the third lens group and, upon zooming from the wide-angleend state to the telephoto end state, a distance between the third lensgroup and the fourth lens group is varied. With this construction, theposition of the principal point of the lens groups from the first tothird lens groups is displaced to the object side, thereby enabling todownsize the variable magnification optical system according to thefirst embodiment of the present application. Also, it is possible tosuppress distortion in the wide-angle end state, and variation ofspherical aberration and variation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that afifth lens group is disposed on the image side of the fourth lens groupand, upon zooming from the wide-angle end state to the telephoto endstate, a distance between the fourth lens group and the fifth lens groupis varied. With this construction, it is possible to suppress distortionin the wide-angle end state, and variation of spherical aberration andvariation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that an Rlens group is disposed on the most image side, and upon zooming from thewide-angle end state to the teleohito end state, the position of the Rlens group is fixed. With this construction, upon zooming, it ispossible to vary the height of marginal light flux incident on the Rlens group from the optical axis, and suppress variation of astigmatism.

Also, it is preferable that the variable magnification optical systemaccording to the first embodiment of the present application satisfiesthe following conditional expression (2):0.280<(−fv)/f3<5.200  (2)where f3 denotes a focal length of the third lens group, and fv denotesthe focal length of the V lens group.

The conditional expression (2) defines the range of the proper focallength ratio of the third lens group and the V lens group. With thevariable magnification optical system according to the first embodimentof the present application satisfying the conditional expression (2), itis possible to suppress decentering coma at the time of carrying outvibration reduction. When the value of (−fv)/f3 in the conditionalexpression (2) according to the variable magnification optical systemaccording to the first embodiment of the present application is equal toor falls down the lower limit value, decentering coma at the time ofcarrying out vibration reduction becomes large. Incidentally, in orderto secure the effect of the present application surely, it is preferableto set the lower limit value of the conditional expression (2) to 0.610.Further, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (2) to 0.740.

On the other hand, when the value of (−fv)/f3 in the conditionalexpression (2) of the variable magnification optical system according tothe first embodiment of the present application is equal to or exceedsthe upper limit value, the moving amount of the V lens group needed atthe time of carrying out vibration reduction becomes large. Accordingly,decentering coma generated by the V lens group becomes large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (2) to 2.400. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (2) to 1.650.

Also, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that thethird lens group includes the V lens group. That is, with the V lensgroup constituting a portion of the third lens group, it is possible tosuppress the moving amount of the V lens group needed at the time ofcarrying out vibration reduction, and suppress decentering comagenerated by the V lens group. Also, it is possible to easily suppressmutual tilt decentering of the third lens group and the V lens groupgenerated at the time of manufacture, and suppress decentering coma andastigmatism generated due to tilt decentering of the V lens group.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that thethird lens group includes a 3A lens group having positive refractivepower on the object side of the V lens group. With this construction, itis possible to suppress the moving amount of the V lens group needed atthe time of carrying out vibration reduction and suppress decenteringcoma generated by the V lens group.

Further, it is preferable that the variable magnification optical systemaccording to the first embodiment of the present application satisfiesthe following conditional expression (3):0.300<(−fv)/f3A<3.800  (3)where f3A denotes a focal length of the 3A lens group, and fv denotesthe focal length of the V lens group.

The conditional expression (3) defines the range of the proper focallength ratio of the 3A lens group and the V lens group. With thevariable magnification optical system according to the first embodimentof the present application satisfying the conditional expression (3), itis possible to suppress decentering coma at the time of carrying outvibration reduction.

When the value of (−fv)/f3A of the conditional expression (3) in thevariable magnification optical system according to the first embodimentof the present application is equal to or falls down the lower limitvalue, decentering coma at the time of carrying out vibration reductionbecomes large. Incidentally, in order to secure the effect of thepresent application surely, it is preferable to set the lower limitvalue of the conditional expression (3) to 0.650. Further, in order tosecure the effect of the present application surely, it is preferable toset the lower limit value of the conditional expression (3) to 0.920.

On the other hand, when the value of (−fv)/f3A in the conditionalexpression (3) of the variable magnification optical system according tothe first embodiment of the present application is equal to or exceedsthe upper limit value, the moving amount of the V lens group needed atthe time of carrying out vibration reduction becomes large. Accordingly,decentering coma generated by the V lens group becomes large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (3) to 3.700. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (3) to 2.900.

Also, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, adistance between the 3A lens group and the V lens group is madeunchangeable. With this construction, it is possible to suppress, uponzooming, change of mutual tilt decentering of the third lens group andthe V lens group generated at the time of manufacture. Therefore, it ispossible to suppress variation of decentering coma and variation ofinclination of astigmatism generated due to tilt decentering of the Vlens group upon zooming.

Also, it is desirable that the variable magnification optical systemaccording to the first embodiment of the present application satisfiesthe following conditional expression (4):0.320<ff/f3<5.200  (4)where f3 denotes the focal length of the third lens group, and ffdenotes the focal length of the F lens group.

The conditional expression (4) defines the range of the proper focallength ratio of the third lens group and the F lens group. With thevariable magnification optical system according to the first embodimentof the present application satisfying the conditional expression (4), itis possible to suppress variation of spherical aberration and variationof astigmatism generated by the F lens group upon focusing.

When the value of ff/f3 in the conditional expression (4) according tothe variable magnification optical system according to the firstembodiment of the present application is equal to or falls down thelower limit value, variation of spherical aberration and variation ofastigmatism generated by the F lens group upon focusing becomes large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (4) to 0.880. Further, in order to secure the effect of thepresent application surely, it is preferable to set the lower limitvalue of the conditional expression (4) to 1.150.

On the other hand, when the value of ff/f3 in the conditional expression(4) of the variable magnification optical system according to the firstembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the F lens group upon focusing becomeslarge. Accordingly, heights of on-axis light rays and off-axis lightrays incident on the F lens group from the optical axis upon focusingare largely varied, so that variation of spherical aberration andvariation of astigmatism generated by the F lens group become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (4) to 2.600. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (4) to 1.900.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that thethird lens group includes the F lens group. That is, with the F lensgroup constituting a portion of the third lens group, it is possible toeasily suppress mutual tilt decentering of the third lens group and theF lens group generated at the time of manufacture, and suppressdecentering coma and astigmatism generated due to tilt decentering ofthe F lens group.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that the Flens group is disposed on the most image side of the third lens group.With this construction, it is possible to suppress variation of thefocal length of the variable magnification optical system of the presentapplication upon focusing, and suppress variation of an angle of viewupon focusing, enabling to achieve high optical performance. Also, it ispossible to suppress the moving amount of the F lens group upon focusingin the telephoto end state. Therefore, it is possible not only todownsize the variable magnification optical system according to thefirst embodiment of the present application but also to suppressvariation of astigmatism and variation of distortion upon focusing.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that an Mlens group having positive refractive power is disposed between the Vlens group and the F lens group. With this construction, it is possibleto suppress decentering coma generated by the V lens group in the statethat the V lens group is moved to have the component in the directionperpendicular to the optical axis at the time of carrying out vibrationreduction. Also, it is possible to suppress the moving amount of the Flens group upon focusing. Therefore, it is possible to suppressvariation of astigmatism and variation of spherical aberration generatedby the F lens group upon focusing.

Further, it is desirable that the variable magnification optical systemaccording to the first embodiment of the present application satisfiesthe following conditional expression (5):0.110<(−fv)/fm<2.600  (5)where fv denotes the focal length of the V lens group, and fm denotes afocal length of the M lens group.

The conditional expression (5) defines the range of the proper focallength ratio of the V lens group and the F lens group. With the variablemagnification optical system according to the first embodiment of thepresent application satisfying the conditional expression (5), it ispossible to suppress decentering coma generated by the V lens group inthe state that the V lens group is moved to have the component in thedirection perpendicular to the optical axis at the time of carrying outvibration reduction. Also, it is possible to suppress variation ofastigmatism and variation of spherical aberration generated by the Flens group upon focusing.

When the value of (−fv)/fm in the conditional expression (5) accordingto the variable magnification optical system according to the firstembodiment of the present application is equal to or falls down thelower limit value, decentering coma generated by the V lens group in thestate that the V lens group is moved to have the component in thedirection perpendicular to the optical axis at the time of carrying outvibration reduction becomes large. Also, the moving amount of the F lensgroup upon focusing becomes large. Accordingly, it becomes difficult tosuppress variation of astigmatism and variation of spherical aberrationgenerated in the F lens group upon focusing. Incidentally, in order tosecure the effect of the present application surely, it is preferable toset the lower limit value of the conditional expression (5) to 0.230.

On the other hand, when the value of (−fv)/fm in the conditionalexpression (5) of the variable magnification optical system according tothe first embodiment of the present application is equal to or exceedsthe upper limit value, the moving amount of the V lens group needed atthe time of carrying out vibration reduction becomes large. Accordingly,decentering coma generated by the V lens group becomes large. Also, itbecomes difficult to suppress variation of astigmatism and variation ofspherical aberration generated in the F lens group upon focusing.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (5) to 1.300. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (5) to 0.880.

Further, it is desirable that the variable magnification optical systemaccording to the first embodiment of the present application satisfiesthe following conditional expression (6):0.080<ff/fm<1.700  (6)where ff denotes the focal length of the F lens group, and fm denotesthe focal length of the M lens group.

The conditional expression (6) defines the range of the proper focallength ratio of the F lens group and the M lens group. With the variablemagnification optical system according to the first embodiment of thepresent application satisfying the conditional expression (6), it ispossible to suppress variation of astigmatism and variation of sphericalaberration generated in the F lens group upon focusing.

When the value of ff/fm in the conditional expression (6) according tothe variable magnification optical system according to the firstembodiment of the present application is equal to or falls down thelower limit value, variation of astigmatism and variation of sphericalaberration generated in the F lens group upon focusing become large.

Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (6) to 0.200.

On the other hand, when the value of ff/fm in the conditional expression(6) of the variable magnification optical system according to the firstembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the F lens group upon focusing becomeslarge. Accordingly, on-axis light rays and off-axis light rays incidenton the F lens group upon focusing are largely varied, so that variationof astigmatism and variation of spherical aberration become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (6) to 1.200. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (6) to 0.950.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thedistance between the first lens group and the second lens groupincreases. With this construction, it is possible to increase themagnification of the second lens group and suppress variation ofspherical aberration and variation of astigmatism upon zooming whileeffectively realizing a high zoom ratio.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that thedistance between the second lens group and the third lens groupdecreases. With this construction, it is possible to increase thecomposite magnification from the third lens group to the lens grouplocated on the most image side, and suppress variation of sphericalaberration and variation of astigmatism upon zooming while effectivelyrealizing a high zoom ratio.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thefirst lens group is moved to the object side. With this construction, itis possible to suppress variation of the height of off-axis rays passingthrough the first lens group from the optical axis, reduce the diameterof the first lens, and suppress variation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thethird lens group is moved to the object side. With this construction, itis possible to increase the magnification of the third lens group, andsuppress variation of spherical aberration and variation of astigmatismgenerated in the third lens group upon zooming.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thesecond lens group is moved along the optical axis. With thisconstruction, upon zooming, it is possible to suppress variation ofastigmatism generated by the first lens group and the third lens groupespecially in the intermediate focal length state.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that thesecond lens group includes, in order from the object side, a first lenshaving negative refractive power, a second lens having positiverefractive power, and a third lens having negative refractive power.With this construction, it is possible to suppress respective variationsof coma, spherical aberration and astigmatism generated in the secondlens group upon zooming. Also, as compared with composing the secondlens group with four or more lenses, it is possible to reduce thethickness of the second lens group, and suppress the height of off-axisrays in the first lens group from the optical axis in the wide-angle endstate thereby to enable downsizing of the first lens group.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that thesecond lens and the third lens are cemented together. With thisconstruction, it is possible to suppress variation of coma generated inthe second lens upon zooming.

Further, in the variable magnification optical system according to thefirst embodiment of the present application, it is desirable that theobject side lens surface of the first lens and the image side surface ofthe third lens are aspherical surfaces. With this construction, it ispossible to suppress respective variations of astigmatism, coma anddistortion upon zooming.

An optical apparatus of the present application is equipped with theabove-constructed variable magnification optical system according to thefirst embodiment. Accordingly, it is possible to realize the compactoptical apparatus with a high zoom ratio and high optical performance.

High optical performance can be achieved upon focusing and even when thelens group is moved to have the component in the direction perpendicularto the optical axis.

A method for manufacturing for the variable magnification optical systemaccording to the first embodiment of the present application, is amethod for manufacturing a variable magnification optical system whichcomprises from an object side: a first lens group having positiverefractive power; a second lens group having negative refractive power;a the third lens group having positive refractive power; the methodcomprising the steps of: disposing a V lens group that has negativerefractive power and that is moved so as to have the component in thedirection perpendicular to the optical axis, and an F lens group thathas positive refractive power and that is moved along the optical axisupon focusing from an infinitely distant object to a close object;disposing the V lens group on a more object side than the F lens group;and constructing such that, upon zooming from a wide-angle end state toa telephoto end state, a distance between the first lens group and thesecond lens group, and a distance between the second lens group and thethird lens group are varied. Accordingly, it is possible to realize thecompact variable magnification optical system with a high zoom ratio andhigh optical performance. High optical performance can be achieved uponfocusing and even when the lens group is moved to have the component inthe direction perpendicular to the optical axis.

Hereinafter, a variable magnification optical according to a secondembodiment of the present application, an optical apparatus and a methodfor manufacturing the variable magnification optical system will beexplained.

The variable magnification optical system according to the secondembodiment of the present application comprises: in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; and a third lens group havingpositive refractive power; upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group being varied, and a distance between the second lensgroup and the third lens group being varied. With this construction, inthe variable magnification optical system according to the secondembodiment of the present application, it is possible to realize zoomingfrom the wide-angle end state to the telephoto end state and suppressvariations of distortion, astigmatism and spherical aberration uponzooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, the third lens groupincludes an F lens group having positive refractive power which is movedalong the optical axis upon focusing from an infinitely distant objectto a close object. With this construction, it is possible to suppressvariation of astigmatism and variation of spherical aberration uponfocusing. Also, it is possible to suppress variation of the focal lengthof the variable magnification optical system according to the secondembodiment of the present application, and suppress variation of theangle of view upon focusing, enabling to realize high opticalperformance. Also, in the telephoto end state, it is possible tosuppress the moving amount of the F lens group upon focusing.Accordingly, it is possible not only to downsize the variablemagnification optical system according to the second embodiment of thepresent application but also to suppress variation of astigmatism andvariation of distortion upon focusing.

With the above construction, it is possible to realize the compactvariable magnification optical system with a high zoom ratio and highoptical performance. High optical performance can be achieved even uponfocusing.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (4):0.320<ff/f3<5.200  (4)where f3 denotes a focal length of the third lens group, and ff denotesa focal length of the F lens group.

The conditional expression (4) defines the range of the proper focallength ratio of the third lens group and the F lens group. With thevariable magnification optical system according to the second embodimentof the present application satisfying the conditional expression (4), itis possible to suppress variation of spherical aberration and variationof astigmatism generated by the F lens group upon focusing.

When the value of ff/f3 in the conditional expression (4) according tothe variable magnification optical system according to the secondembodiment of the present application is equal to or falls down thelower limit value, variation of spherical aberration and variation ofastigmatism generated by the F lens group upon focusing becomes large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (4) to 0.880. Further, in order to secure the effect of thepresent application surely, it is preferable to set the lower limitvalue of the conditional expression (4) to 1.150.

On the other hand, when the value of ff/f3 in the conditional expression(4) of the variable magnification optical system according to the secondembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the F lens group upon focusing becomeslarge. Accordingly, heights of on-axis light rays and off-axis lightrays incident on the F lens group from the optical axis upon focusingare largely varied, so that variation of spherical aberration andvariation of astigmatism generated by the F lens group become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (4) to 2.600. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (4) to 1.900.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that the Flens group is a portion lens group of the third lens group. With thisconstruction, that is, the F lens group being a portion of the thirdlens group, it is possible to suppress variation of the focal length ofthe variable magnification optical system according to the secondembodiment of the present application upon focusing, and suppressvariation of astigmatism and the like upon focusing.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that the Flens group is disposed on the most image side of the third lens group.With this construction, it is possible to suppress variation of thefocal length of the variable magnification optical system according tothe second embodiment of the present application upon focusing, andsuppress variation of angle of view upon focusing thereby to enablerealizing high optical performance. Also, it is possible to suppressvariation of astigmatism and variation of distortion upon focusing.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that afourth lens group having negative refractive power is disposed on theimage side of the third lens group and, upon zooming from the wide-angleend state to the telephoto end state, a distance between the third lensgroup and the fourth lens group is varied. With this construction, theposition of the principal point of the lens groups from the first to thethird lens groups is displaced to the object side, so that it ispossible to downsize the variable magnification optical system accordingto the second embodiment of the present application. Also, it ispossible to suppress distortion in the wide-angle end state, andsuppress variation of spherical aberration and variation of astigmatismupon zooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that afifth lens group is disposed on the image side of the fourth lens groupand, upon zooming from the wide-angle end state to the telephoto endstate, a distance between the fourth lens group and fifth lens group isvaried. With this construction, it is possible to suppress distortion inthe wide-angle end state, and suppress variation of spherical aberrationand variation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that an Rlens group is disposed on the most image side and, upon zooming from thewide-angle end state to the telephoto end state, the position of the Rlens group is fixed.

With this construction, upon zooming, the height of marginal light fluxincident on the R lens from the optical axis is varied, so that it ispossible to suppress variation of astigmatism.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (7):5.500<f1/fw<9.000  (7)where fw denotes the focal length of the variable magnification opticalsystem in the wide-angle end state, and f1 is a focal length of thefirst lens group.

The conditional expression (7) defines the range of the proper focallength of the first lens group. With the variable magnification opticalsystem according to the second embodiment of the present applicationsatisfying the conditional expression (7), it is possible to suppressvariation of spherical aberration and variation of astigmatism uponzooming.

When the value of f1/fw in the conditional expression (7) according tothe variable magnification optical system according to the secondembodiment of the present application is equal to or falls down thelower limit value, it becomes difficult to suppress variation ofspherical aberration and variation of astigmatism generated in the firstlens group upon zooming, so that high optical performance cannot beachieved. Incidentally, in order to secure the effect of the presentapplication surely, it is preferable to set the lower limit value of theconditional expression (7) to 6.700. Further, in order to secure theeffect of the present application surely, it is preferable to set thelower limit value of the conditional expression (7) to 7.300.

On the other hand, when the value of f1/fw in the conditional expression(7) of the variable magnification optical system according to the secondembodiment of the present application is equal to or exceeds the upperlimit value, it is necessary to increase the amount of change of thedistance between the first lens group and the second lens group uponzooming in order to obtain a predetermined zoom ratio. Accordingly, itbecome difficult to downsize the variable magnification optical systemaccording to the second embodiment of the present application and theratio of the diameter of on-axis light rays incident on the first lensgroup and the diameter of on-axis light rays incident on the second lensgroup is varied largely upon zooming. Accordingly, variation ofspherical aberration upon zooming becomes large, so that high opticalperformance cannot be realized. Incidentally, in order to secure theeffect of the present application surely, it is preferable to set theupper limit value of the conditional expression (7) to 8.500. Further,in order to secure the effect of the present application surely, it ispreferable to set the upper limit value of the conditional expression(7) to 8.200.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that thethird lens group includes a V lens having negative refractive powerwhich is moved so as to have a component in a direction perpendicular tothe optical axis. In the variable magnification optical system accordingto the second embodiment of the present application, with the V lensgroup being moved to have the component in the direction perpendicularto the optical axis, it is possible to move an image and correct animage blur due to a camera shake, in other words, carry out vibrationreduction. Also, with the above-mentioned construction, it is possibleto suppress decentering coma generated in the V lens group.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that the Vlens group is disposed on the more object side than the F lens group.With this construction, the ratio of the moving amount of an image tothe moving amount of the V lens group can be made large in the telephotoend state rather than in the wide-angle end state. Accordingly, it ispossible to suppress the moving amount of the V lens group to be neededin the telephoto end state, and suppress decentering coma generated inthe V lens group.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (1):0.240<ff/(−fv)<4.000  (1)where ff denotes a focal length of the F lens group, and fv denotes afocal length of the V lens group.

The conditional expression (1) defines the range of the proper focallength ratio of the F lens group and the V lens group. With the variablemagnification optical system according to the second embodiment of thepresent application satisfying the conditional expression (1), it ispossible to suppress decentering coma at the time when vibrationreduction is carried out by moving the V lens group in the directionperpendicular to the optical axis. Also, it is possible to suppressvariation of spherical aberration and variation of astigmatism to begenerated in each lens group upon focusing.

When the value of ff/(−fv) in the conditional expression (1) accordingto the variable magnification optical system according to the secondembodiment of the present application is equal to or falls down thelower limit value, variation of spherical aberration and variation ofastigmatism generated in each lens group upon focusing become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (1) to 0.490. Further, in order to secure the effect of thepresent application surely, it is preferable to set the lower limitvalue of the conditional expression (1) to 0.630.

On the other hand, the value of ff/(−fv) in the conditional expression(1) of the variable magnification optical system according to the secondembodiment of the present application is equal to or exceeds the upperlimit value, decentering coma upon conducting vibration reductionbecomes large. Also, the moving amount of the F lens group upon focusingbecomes large. Therefore, upon focusing, the state of light passingthrough the F lens group is largely changed, and it becomes impossibleto suppress variation of spherical aberration and variation ofastigmatism generated in the F lens group. Incidentally, in order tosecure the effect of the present application surely, it is preferable toset the upper limit value of the conditional expression (1) to 2.800.Further, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (1) to 1.800.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (2):0.280<(−fv)/f3<5.200  (2)where f3 denotes a focal length of the third lens group, and fv denotesthe focal length of the V lens group.

The conditional expression (2) defines the range of the proper focallength ratio of the third lens group and the V lens group. With thevariable magnification optical system according to the second embodimentof the present application satisfying the conditional expression (2), itis possible to suppress decentering coma at the time of carrying outvibration reduction.

When the value of (−fv)/f3 in the conditional expression (2) accordingto the variable magnification optical system according to the secondembodiment of the present application is equal to or falls down thelower limit value, decentering coma at the time of carrying outvibration reduction becomes large. Incidentally, in order to secure theeffect of the present application surely, it is preferable to set thelower limit value of the conditional expression (2) to 0.610. Further,in order to secure the effect of the present application surely, it ispreferable to set the lower limit value of the conditional expression(2) to 0.740.

On the other hand, the value of (−fv)/f3 in the conditional expression(2) of the variable magnification optical system according to the firstembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the V lens group needed at the time ofcarrying out vibration reduction becomes large. Accordingly, decenteringcoma generated by the V lens group becomes large. Incidentally, in orderto secure the effect of the present application surely, it is preferableto set the upper limit value of the conditional expression (2) to 2.400.Further, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (2) to 1.650.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that thethird lens group includes a 3A lens group having positive refractivepower on the object side of the V lens group. With this construction, itis possible to suppress the moving amount of the V lens group to beneeded at the time of carrying out vibration reduction and suppressdecentering coma generated by the V lens group.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (3):0.300<(−fv)/f3A<3.800  (3)where f3A denotes a focal length of the 3A lens group, and fv denotesthe focal length of the V lens group.

The conditional expression (3) defines the range of the proper focallength ratio of the 3A lens group and the V lens group. With thevariable magnification optical system according to the second embodimentof the present application satisfying the conditional expression (3), itis possible to suppress decentering coma at the time of carrying outvibration reduction.

When the value of (−fv)/f3A in the expression (3) according to thevariable magnification optical system according to the second embodimentof the present application is equal to or falls down the lower limitvalue, decentering coma at the time of carrying out vibration reductionbecomes large. Incidentally, in order to secure the effect of thepresent application surely, it is preferable to set the lower limitvalue of the conditional expression (3) to 0.650. Further, in order tosecure the effect of the present application surely, it is preferable toset the lower limit value of the conditional expression (3) to 0.920.

On the other hand, the value of (−fv)/f3A in the conditional expression(3) of the variable magnification optical system according to the secondembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the V lens group needed at the time ofcarrying out vibration reduction becomes large. Accordingly, decenteringcoma generated by the V lens group becomes large. Incidentally, in orderto secure the effect of the present application surely, it is preferableto set the upper limit value of the conditional expression (3) to 3.700.Further, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (3) to 2.900.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, adistance between the 3A lens group and the V lens group is madeunchangeable. With this construction, it is possible to suppress, uponzooming, change of mutual tilt decentering of the third lens group andthe V lens group generated at the time of manufacture. Therefore, it ispossible to suppress variation of decentering coma and variation ofinclination of astigmatism generated due to tilt decentering of the Vlens group upon zooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that thethird lens group includes an M lens group having positive refractivepower between the V lens group and the F lens group. With thisconstruction, it is possible to suppress decentering coma generated bythe V lens group in the state that the V lens group is moved to have thecomponent in the direction perpendicular to the optical axis at the timeof carrying out vibration reduction. Also, it is possible to suppressthe moving amount of the F lens group upon focusing. Therefore, it ispossible to suppress variation of astigmatism and variation of sphericalaberration generated by the F lens group upon focusing.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (5):0.110<(−fv)/fm<2.600  (5)where fm denotes a focal length of the M lens group, and fv denotes thefocal length of the V lens group.

The conditional expression (5) defines the range of the proper focallength ratio of the V lens group and the F lens group. With the variablemagnification optical system according to the second embodiment of thepresent application satisfying the conditional expression (5), it ispossible to suppress decentering coma generated by the V lens group inthe state that the V lens group is moved to have the component in thedirection perpendicular to the optical axis at the time of carrying outvibration reduction. Also, it is possible to suppress variation ofastigmatism and variation of spherical aberration generated by the Flens group upon focusing.

When the value of (−fv)/fm in the conditional expression (5) accordingto the variable magnification optical system according to the firstembodiment of the present application is equal to or falls down thelower limit value, decentering coma generated by the V lens group in thestate that the V lens group is moved to have the component in thedirection perpendicular to the optical axis at the time of carrying outvibration reduction becomes large. Also, the moving amount of the F lensgroup upon focusing becomes large. Accordingly, it becomes difficult tosuppress variation of astigmatism and variation of spherical aberrationgenerated in the F lens group upon focusing. Incidentally, in order tosecure the effect of the present application surely, it is preferable toset the lower limit value of the conditional expression (5) to 0.230.

On the other hand, the value of (−fv)/fm in the conditional expression(5) of the variable magnification optical system according to the firstembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the V lens group needed at the time ofcarrying out vibration reduction becomes large. Accordingly, decenteringcoma generated by the V lens group becomes large. Also, it becomesdifficult to suppress variation of astigmatism and variation ofspherical aberration generated in the F lens group upon focusing.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (5) to 1.300. Further, in order to secure the effect of thepresent application surely, it is preferable to set the upper limitvalue of the conditional expression (5) to 0.880.

Further, it is desirable that the variable magnification optical systemaccording to the second embodiment of the present application satisfiesthe following conditional expression (6):0.080<ff/fm<1.700  (6)where ff denotes the focal length of the F lens group, and fm denotesthe focal length of the M lens group.

The conditional expression (6) defines the range of the proper focallength ratio of the F lens group and the M lens group. With the variablemagnification optical system according to the second embodiment of thepresent application satisfying the conditional expression (6), it ispossible to suppress variation of astigmatism and variation of sphericalaberration generated in the F lens group upon focusing.

When the value of ff/fm in the conditional expression (6) according tothe variable magnification optical system according to the secondembodiment of the present application is equal to or falls down thelower limit value, variation of astigmatism and variation of sphericalaberration generated in the F lens group upon focusing become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (6) to 0.200.

On the other hand, when the value of ff/fm in the conditional expression(6) of the variable magnification optical system according to the secondembodiment of the present application is equal to or exceeds the upperlimit value, the moving amount of the F lens group upon focusing becomeslarge. Accordingly, on-axis light rays and off-axis light rays incidenton the F lens group upon focusing are largely varied, so that variationof astigmatism and variation of spherical aberration become large.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (6) to 1.200. Further, in order to secure the effect of thepresent application surely, it is more preferable to set the upper limitvalue of the conditional expression (6) to 0.950.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thedistance between the first lens group and the second lens groupincreases. With this construction, it is possible to increase themagnification of the second lens group and suppress variation ofspherical aberration and variation of astigmatism upon zooming whileeffectively realizing a high zoom ratio.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that thedistance between the second lens group and the third lens groupdecreases. With this construction, it is possible to increase thecomposite magnification from the third lens group to the lens grouplocated on the most image side, and suppress variation of sphericalaberration and variation of astigmatism upon zooming while effectivelyrealizing a high zoom ratio.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thefirst lens group is moved to the object side. With this construction, itis possible to suppress variation of the height of off-axis rays passingthrough the first lens group from the optical axis, reduce the diameterof the first lens, and suppress variation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thethird lens group is moved to the object side. With this construction, itis possible to increase the magnification of the third lens group, andsuppress variation of spherical aberration and variation of astigmatismgenerated in the third lens group upon zooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thesecond lens group is moved along the optical axis. With thisconstruction, upon zooming, it is possible to suppress variation ofastigmatism generated by the first lens group and the third lens groupespecially in the intermediate focal length state.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that thesecond lens group includes, in order from the object side, a first lenshaving negative refractive power, a second lens having positiverefractive power, and a third lens having negative refractive power.With this construction, it is possible to suppress respective variationsof coma, spherical aberration and astigmatism generated in the secondlens group upon zooming. Also, as compared with composing the secondlens group with four or more lenses, it is possible to reduce thethickness of the second lens group, and suppress the height of off-axislight rays in the first lens group from the optical axis in thewide-angle end state thereby to enable downsizing of the first lensgroup.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that thesecond lens and the third lens are cemented together. With thisconstruction, it is possible to suppress variation of coma generated inthe second lens upon zooming.

Further, in the variable magnification optical system according to thesecond embodiment of the present application, it is desirable that anobject side lens surface of the first lens and an image side surface ofthe third lens are aspherical surfaces. With this construction, it ispossible to suppress respective variations of astigmatism, coma anddistortion upon zooming.

An optical apparatus of the present application is equipped with theabove-constructed variable magnification optical system according to thesecond embodiment. Accordingly, it is possible to realize the compactoptical apparatus with a high zoom ratio and high optical performance.

High Optical Performance can be Achieved Even Upon Focusing.

A method for manufacturing for the variable magnification optical systemaccording to the second embodiment of the present application, is amethod for manufacturing a variable magnification optical system whichcomprises from an object side: a first lens group having positiverefractive power; a second lens group having negative refractive power;and a third lens group having positive refractive power; the methodcomprising the steps of: constructing the third lens group to include anF lens group having positive refractive power and being moved along theoptical axis upon focusing from an infinitely distant object to a closeobject; and constructing such that, upon zooming from a wide-angle endstate to a telephoto end state, a distance between the first lens groupand the second lens group and a distance between the second lens groupand the third lens group are varied. Accordingly, it is possible tomanufacture the compact variable magnification optical system with ahigh zoom ratio and high optical performance. High optical performancecan be achieved even upon focusing.

Hereinafter, a variable magnification optical system according to athird embodiment of the present application, an optical apparatustherewith and a method for manufacturing the variable magnificationoptical system will be explained.

The variable magnification optical system according to the thirdembodiment of the present application comprises: in order from an objectside: a first lens group having positive refractive power; a second lensgroup having negative refractive power; a third lens group havingpositive refractive power; a fourth lens group having negativerefractive power; and fifth lens group having positive refractive power,upon zooming from a wide-angle end state to a telephoto end state, adistance between the first lens group and the second lens group, adistance between the second lens group and the third lens group, adistance between the third lens group and the fourth lens group and adistance between the fourth lens group and the fifth lens group beingvaried. With this construction, in the variable magnification opticalsystem according to the third embodiment of the present application, itis possible to realize zooming from the wide-angle end state to thetelephoto end state and suppress respective variations of distortion,astigmatism and spherical aberration upon zooming.

Further, in the variable magnification optical system according to thethird embodiment of the present application, upon zooming from thewide-angle end state to the telephoto end state, the first lens group ismoved along the optical axis. With this construction, it is possible tosuppress variation of the height of off-axis light rays passing throughthe first lens group from the optical axis upon zooming. Accordingly, itis possible to reduce the diameter of the first lens group and suppressvariation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thethird embodiment of the present application, upon zooming from thewide-angle end state to the telephoto end state, the position of thefifth lens group is fixed. With this construction, it is possible tovary a height of marginal light rays incident on the fifth lens groupfrom the fourth lens group upon zooming. Accordingly, it is possible tosuppress well variation of astigmatism upon zooming.

Further, the variable magnification optical system according to thethird embodiment of the present application satisfies the followingconditional expression (8):0.170<(−f4)/f5<0.400  (8)where f4 denotes a focal length of the fourth lens group, and f5 denotesa focal length of the fifth lens group.

The conditional expression (8) defines the range of the proper focallength ratio of the fourth lens group and the fifth lens group. With thevariable magnification optical system according to the third embodimentof the present application satisfying the conditional expression (8), itis possible to suppress variations of astigmatism and distortion uponzooming.

When the value of (−f4)/f5 in the conditional expression (8) accordingto the variable magnification optical system according to the thirdembodiment of the present application is equal to or falls down thelower limit value, it becomes difficult to suppress variations ofastigmatism and distortion generated in the fourth lens group uponzooming with the fifth lens group, so that high optical performancecannot be achieved. Incidentally, in order to secure the effect of thepresent application surely, it is preferable to set the lower limitvalue of the conditional expression (8) to 0.215.

On the other hand, when the value of (−f4)/f5 in the conditionalexpression (8) of the variable magnification optical system according tothe third embodiment of the present application is equal to or exceedsthe upper limit value, it becomes difficult to suppress variation ofastigmatism generated in the fifth lens group upon zooming, so that highoptical performance cannot be achieved. Incidentally, in order to securethe effect of the present application surely, it is preferable to setthe upper limit value of the conditional expression (8) to 0.300.Further, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (8) to 0.280.

With this construction, it is possible to achieve the compact variablemagnification optical system with a high zoom ratio and high opticalperformance.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thethird lens group is moved to the object side. With this construction, itis possible to increase the magnification of the third lens group, andsuppress variations of spherical aberration and astigmatism generated inthe third lens group upon zooming.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thefourth lens group is moved to the object side. With this construction,it is possible to suppress variation of coma and variation ofastigmatism generated in the fourth lens group upon zooming.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thefirst lens group is moved to the object side. With this construction, itis possible to suppress variation of the height of off-axis light rayspassing through the first lens group upon zooming. Accordingly, it ispossible to reduce the diameter of the first lens group, and suppressvariation of astigmatism upon zooming.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thesecond lens group is moved along the optical axis. With thisconstruction, upon zooming, it is possible to suppress variation ofastigmatism generated by the first lens group and the third lens groupespecially in the intermediate focal length state.

Further, it is desirable that the variable magnification optical systemaccording to the third embodiment of the present application satisfiesthe following conditional expression (7):5.500<f1/fw<9.000  (7)where fw denotes a focal length of the variable magnification opticalsystem in the wide-angle end state, and f1 denotes a focal length of thefirst lens group.

The conditional expression (7) defines the range of the proper focallength of the first lens group. With the variable magnification opticalsystem according to the third embodiment of the present applicationsatisfying the conditional expression (7), it is possible to suppressvariation of spherical aberration and variation of astigmatism uponzooming.

When the value of f1/fw in the conditional expression (7) according tothe variable magnification optical system according to the thirdembodiment of the present application is equal to or falls down thelower limit value, it becomes difficult to suppress variation ofspherical aberration and variation of astigmatism generated in the firstlens group upon zooming, so that high optical performance cannot beachieved. Incidentally, in order to secure the effect of the presentapplication surely, it is preferable to set the lower limit value of theconditional expression (7) to 6.700. Further, in order to secure theeffect of the present application surely, it is preferable to set thelower limit value of the conditional expression (7) to 7.300.

On the other hand, when the value of f1/fw in the conditional expression(7) of the variable magnification optical system according to the thirdembodiment of the present application is equal to or exceeds the upperlimit value, it is necessary to increase the amount of change of thedistance between the first lens group and the second lens group uponzooming in order to obtain a predetermined zoom ratio. Accordingly, itbecomes difficult to downsize the variable magnification optical systemaccording to the third embodiment of the present application, and theratio of the diameter of on-axis light rays incident on the first lensgroup and the diameter of on-axis light rays incident on the second lensgroup is varied largely upon zooming. Accordingly, variation ofspherical aberration upon zooming becomes large, so that high opticalperformance cannot be realized. Incidentally, in order to secure theeffect of the present application surely, it is preferable to set theupper limit value of the conditional expression (7) to 8.500. Further,in order to secure the effect of the present application surely, it ispreferable to set the upper limit value of the conditional expression(7) to 8.200.

Further, it is desirable that the variable magnification optical systemaccording to the third embodiment of the present application satisfiesthe following conditional expression (9):10.500<f5/fw<30.000  (9)where fw denotes the focal length of the variable magnification opticalsystem, and f5 denotes a focal length of the fifth lens group.

The conditional expression (9) defines the range of the proper focallength of the fifth lens group. With the variable magnification opticalsystem according to the third embodiment of the present applicationsatisfying the conditional expression (9), it is possible to suppressvariation of astigmatism and variation of distortion upon zooming.

When the value of f5/fw in the conditional expression (9) according tothe third embodiment of the present application is equal to or fallsdown the lower limit value, it becomes difficult to suppress variationof astigmatism generated in the fifth lens group upon zooming. Also, thediameter of the fifth lens group becomes large. Incidentally, in orderto secure the effect of the present application surely, it is preferableto set the lower limit value of the conditional expression (9) to12.000.

On the other hand, when the value of f5/fw in the conditional expression(9) of the variable magnification optical system according to the thirdembodiment of the present application is equal to or exceeds the upperlimit value, it becomes difficult to suppress variation of astigmatismand variation of distortion generated from the first lens group to thefourth lens group upon zooming with the fifth lens group. Also, thecomposite focal length from the first lens group to the fourth lensgroup becomes small. Accordingly, influence such as decentering coma andthe like caused by decentering among the lenses generated from the firstlens group to the fourth lens group at the time of manufacture becomesrelatively large, so that it becomes difficult to realize high opticalperformance. Incidentally, in order to secure the effect of the presentapplication surely, it is preferable to set the upper limit value of theconditional expression (9) to 28.000.

Further, the optical system according to the third embodiment of thepresent application desirably satisfies the following conditionalexpression (10):0.150<(d4t−d4w)/ft<0.350  (10)where ft denotes the focal length of the variable magnification opticalsystem in the telephoto end state, d4w denotes a vertex distance betweenthe most image side lens surface of the fourth lens group and the mostobject side lens surface of the fifth lens group in the wide-angle endstate, and d4t denotes a vertex distance between the most image sidelens surface of the fourth lens group and the most object side lenssurface of the fifth lens group in the telephoto end state.

The conditional expression (10) defines a range of a proper changeamount of the vertex distance between the most image side lens surfaceof the fourth lens group and the most object side lens surface of thefifth lens group upon zooming. With the variable magnification opticalsystem according to the third embodiment of the present applicationsatisfying the conditional expression (10), it is possible to suppressvariation of astigmatism upon zooming.

When the value of (d4t−d4w)/ft in the conditional expression (10)according to the third embodiment of the present application is equal toor falls down the lower limit value, the focal length of each lens groupfrom the first lens group to the third group needs to be reduced inorder to secure a predetermined zoom ratio. Accordingly, it becomesdifficult to suppress variation of astigmatism generated from the firstlens group to the third lens group upon zooming. Incidentally, in orderto secure the effect of the present application surely, it is preferableto set the lower limit value of the conditional expression (10) to0.175. Further, in order to secure the effect of the present applicationsurely, it is preferable to set the lower limit value of the conditionalexpression (10) to 0.230.

On the other hand, when the value of (d4t−d4w)/ft in the conditionalexpression (10) of the variable magnification optical system accordingto the third embodiment of the present application is equal to orexceeds the upper limit value, it becomes difficult to suppressvariation of astigmatism generated in the fifth lens group upon zooming.Incidentally, in order to secure the effect of the present applicationsurely, it is preferable to set the upper limit value of the conditionalexpression (10) to 0.290.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that, uponzooming from the wide-angle end state to the telephoto end state, thedistance between the first lens group and the second lens groupincreases. With this construction, it is possible to increase themagnification of the second lens group and suppress variation ofspherical aberration and variation of astigmatism upon zooming whileeffectively realizing a high zoom ratio.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that thedistance between the second lens group and the third lens groupdecreases. With this construction, it is possible to increase thecomposite magnification from the third lens group to the fifth lensgroup, and suppress variation of spherical aberration and variation ofastigmatism upon zooming while effectively realizing a high zoom ratio.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that thesecond lens group includes, in order from the object side, a first lenshaving negative refractive power, a second lens having positiverefractive power, and a third lens having negative refractive power.With this construction, it is possible to suppress respective variationsof coma, spherical aberration and astigmatism generated in the secondlens group upon zooming. Also, as compared with composing the secondlens group with four or more lenses, it is possible to reduce thethickness of the second lens group, and suppress the height of off-axisrays in the first lens group from the optical axis in the wide-angle endstate thereby to enable downsizing of the first lens group.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that thesecond lens and the third lens are cemented together. With thisconstruction, it is possible to suppress variation of coma generated inthe second lens upon zooming.

Further, in the variable magnification optical system according to thethird embodiment of the present application, it is desirable that anobject side lens surface of the first lens and an image side surface ofthe third lens are aspherical surfaces. With this construction, it ispossible to suppress respective variations of astigmatism, coma anddistortion upon zooming.

An optical apparatus of the present application is equipped with theabove-constructed variable magnification optical system according to thethird embodiment. Accordingly, it is possible to realize the compactoptical apparatus with a high zoom ratio and high optical performance.

High optical performance can be achieved upon focusing and even when thelens group is moved to have the component in the direction perpendicularto the optical axis.

A method for manufacturing in the variable magnification optical systemaccording to the third embodiment of the present application, is amethod for manufacturing a variable magnification optical system whichcomprises from an object side: a first lens group having positiverefractive power; a second lens group having negative refractive power;a third lens group having positive refractive power; a fourth lens grouphaving negative refractive power and a fifth lens group having positiverefractive power; the method comprising the steps of:

constructing the fourth lens group and the fifth lens group so as tosatisfy the following conditional expression (8):0.170<(−f4)/f5<0.400  (8)

where f4 denotes the focal length of the fourth lens group, and the f5denotes the focal length of the fifth lens group; and

constructing such that, upon zooming from a wide-angle end state to atelephoto end state, a distance between the first lens group and thesecond lens group, a distance between the second lens group and thethird lens group, a distance between the third lens group and the fourthlens group and a distance between the fourth lens group and the fifthlens group are varied; the first lens group is moved along the opticalaxis; and the position of the fifth lens group is fixed.

Accordingly, it is possible to manufacture the compact variablemagnification optical system with a high zoom ratio and high opticalperformance.

Hereinafter, a variable magnification optical system according to eachnumerical example of the first to third embodiments of the presentapplication will be explained with reference to accompanying drawings.The first and second examples are common to all the first to thirdembodiments.

First Example

FIGS. 1A, 1B and 1C are sectional views showing a wide-angle end state,an intermediate focal length state and a telephoto end state of avariable magnification optical system according to the first examplecommon to the first to third embodiment.

The variable magnification optical system according to the first exampleis composed of, in order from an object side: a first lens group G1having positive refractive power; a second lens group G2 having negativerefractive power; a third lens group G3 having positive refractivepower; a fourth lens group G4 having negative refractive power; and afifth lens group G5 having positive refractive power which is an R lensgroup.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 with a convexsurface facing the object side cemented with a biconvex positive lensL12, and a positive meniscus lens L13 with a convex surface facing theobject side.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 with a convex surface facing the object sidewhich is a first lens, and a cemented lens constructed by a positivemeniscus lens L22 with a concave surface facing the object side which isa second lens cemented with a negative meniscus lens L23 with a concavesurface facing the object side which is a third lens. The negativemeniscus lens L21 is a compound type aspherical lens whose object sideglass surface is provided with a resin layer so as to be an asphericalshape. The negative meniscus lens L23 is a glass mold type asphericallens whose image side lens surface is made to be an aspherical shape.

The third lens group G3 is composed of, in order from the object side, a3A lens group G3A having positive refractive power, a V lens group GVhaving negative refractive power, an M lens group GM having positiverefractive power and an F lens group GF having positive refractivepower.

The 3A lens group G3A consists of, in order from the object side, apositive meniscus lens L31 with convex surface facing the object side,and a biconvex positive lens L32.

The V lens group GV consists of, in order from the object side, acemented lens constructed by a positive meniscus lens L33 with a concavesurface facing the object side cemented with a biconcave negative lensL34. The negative lens L34 is a glass mold type aspherical lens whoseimage side lens surface is made to be an aspherical shape.

The M lens group GM consists of, in order from the object side, acemented lens constructed by a biconvex positive lens L35 cemented witha negative meniscus lens L36 with concave surface facing the object sideand a negative meniscus lens L37 with a concave surface facing theobject side. The negative meniscus lens L37 is a glass mold typeaspherical lens whose image side lens surface is made to be anaspherical shape.

The F lens group GF consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L38 with convexsurface facing the object side cemented with a biconvex positive lensL39.

An aperture stop S is disposed on the object side of the third lensgroup G3.

The fourth lens group G4 consists of, in order from the object side, abiconcave negative lens L41, a negative meniscus lens L42 with a concavesurface facing the object side and a biconvex positive lens L43.

The fifth lens group G5 consists of a positive meniscus lens L51 with aconcave surface facing the object side. The positive meniscus lens L51is a glass mold type aspherical lens whose image side lens surface ismade to be an aspherical shape.

With the above-mentioned construction, in the variable magnificationoptical system according to the present example, upon zooming from thewide-angle end state to the telephoto end state, the first to the fourthlens groups G1 to G4 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4and a distance between the fourth lens group G4 and the fifth lens G5group are varied.

Specifically, the lens first group G1 to the fourth lens group G4 aremoved to the object side upon zooming. The position of the fifth lensgroup G5 is fixed in a direction of the optical axis upon zooming. Theaperture stop S is moved integrally with the third lens group G3 to theobject side upon zooming.

Accordingly, upon zooming, the distance between the first lens group G1and the second lens group G2 increases, the distance between the secondlens group G2 and the third lens group G3 decreases, and the distancebetween the fourth lens group G4 and the fifth lens group G5 increases.Also, upon zooming, the distance between the third lens group G3 and thefourth lens group G4 increases from the wide-angle end state to theintermediate focal length state, and decreases from the intermediatefocal length state to the telephoto end state. A distance between the 3Alens group G3A and the V lens group GV of the third lens group G3 isconstant upon zooming.

Further, in the variable magnification optical system according to thepresent example, at the time of occurrence of a camera shake, the V lensgroup of the third lens group G3 is used as a vibration reduction lensgroup and moved so as to have a component in a direction perpendicularto the optical axis thereby to carry out vibration reduction.

Further, in the variable magnification optical system according to thepresent example, the F lens group of the third lens group G3 is used asa focusing lens group and moved along the optical axis to the objectside thereby to carry out focusing from an infinitely distant object toa close object.

Table 1 below shows various values associated with the variablemagnification optical system according to the present example.

In Table 1, f denotes a focal length, and BF denotes a back focallength, that is, denotes a distance between the most image side lenssurface and the image plane I on the optical axis.

In [Surface Data] m denotes an order of an optical surface counted fromthe object side, r denotes a radius of curvature, d denotes asurface-to-surface distance (an interval from an n-th surface to an(n+1)-th surface, where n is an integer.), nd denotes a refractive indexto d-line (wavelength=587.6 nm), and νd denotes an Abbe number to d-line(wavelength=587.6). OP denotes an object surface, and I denotes theimage plane. The radius of curvature r=∞ indicates a plane surface. “*”mark is attached to a surface number of each aspherical surface, and avalue of each paraxial radius of curvature is listed in the column ofthe radius of curvature r. The refractive index of air nd=1.000000 isomitted.

[Aspherical Data] shows aspherical surface coefficients and conicconstants in the case when the shape of each aspherical surface shown in[Surface Data] is expressed by the following expression:

x = (h²/r)/[1 + {1 − κ(h/r)²}^(1/2)] + A 4h⁴ + A 6h⁶ + A 8h⁸ + A 10h¹⁰ + A 12h¹²

Here, h is made to be a height vertical to the optical axis, x is madeto be a sag amount being the distance between a tangent plane of thevertex of each aspherical surface in the height h to each asphericalsurface along the optical axis, κ is made to be a conic constant, A4,A6, A8, A10, A12 are made to be aspherical surface coefficients, and ris made to be a paraxial radius of curvature being a radius of curvatureof reference sphere. “E-n” (n is an integer) represents “×10^(−n)”. Forexample, “1.234E-05” represents “1.234×10⁻⁵”. The aspherical surfacecoefficient A2 of second order is 0 and is omitted.

In [Various Data], FNO denotes an F number, ω denotes a half angle ofview (unit is “º”), Y denotes an image height, TL denotes a total lengthof the variable magnification optical system, that is, the distancebetween a first surface and the image plane I along the optical axisupon focusing the infinitely distant object, do denotes a variableinterval between an n-th surface and an (n+1)-th surface, and φ denotesthe diameter of the aperture stop S. W denotes the wide-angle end state,M denotes the intermediate focal length and T denotes the telephoto endstate.

[Moving Amount of Focusing Lens Group upon Focusing] shows the movingamount of the F lens group GF upon focusing (shootingmagnification—0.0100 times) from the infinitely distant object to theclose object. The sign of the moving amount is made to be a plus in thecase where the F lens group is moved to the object side. Also, aphotographing distance represents the distance between the objectsurface to the image plane I.

[Lens Group Data] shows a starting surface ST of each lens group and afocal length f.

[Vibration Reduction Coefficient] shows a vibration reductioncoefficient that is a ratio of the moving amount of an image on theimage plane I to the moving amount of the V lens group GV that is thevibration reduction lens group from the optical axis.

[Values for Conditional Expressions] shows corresponding values forconditional expressions of the variable magnification optical systemaccording to the present application.

“mm” is used as the unit for various lengths such as the focal length f,the radius of curvature r and the like. However, even when the opticalsystem is proportionally enlarged or proportionally reduced, the sameoptical performance can be obtained, so the unit is not necessarilylimited to “mm”.

TABLE 1 First Example [Surface Data] m r d nd νd OP ∞  1 140.5647 1.63501.903660 31.27  2 45.6913 7.6885 1.497820 82.57  3 −284.3669 0.1000  444.8550 4.5326 1.804000 46.60  5 209.3179 d5  *6 500.0000 0.10001.553890 38.09  7 190.3219 1.0000 1.883000 40.66  8 8.9187 4.3652  9−114.5251 4.6494 1.808090 22.74 10 −9.8911 1.0000 1.851350 40.10 *11 −141.3941 d11 12 ∞ 1.0000 Aperture Stop S 13 22.3603 1.7845 1.58913061.22 14 187.8269 0.2763 15 15.7519 1.9659 1.487490 70.31 16 −148.61181.8000 17 −28.8021 2.7134 1.903660 31.27 18 −9.8324 1.0000 1.80139045.46 *19  41.1794 1.8000 20 37.0997 2.9939 1.593190 67.90 21 −10.23171.0000 2.000690 25.46 22 −15.2899 0.1000 23 −37.4207 1.6662 1.85135040.10 *24  −4390.3946 5.9000 25 15.4513 1.0000 2.001000 29.14 26 10.65013.5906 1.618000 63.34 27 −71.8553 d27 28 −69.6397 1.0000 1.883000 40.6629 20.2769 1.8596 30 −24.0135 1.0000 1.902650 35.73 31 −41.9476 0.201132 29.1388 2.4495 1.698950 30.13 33 −43.6887 d33 34 −46.1581 0.99981.583130 59.44 *35  −30.3822 BF I ∞ [Aspherical Data] m 6 κ −8.90440 A4 2.59493E−05 A6 −1.90094E−08 A8 −1.65609E−09 A10  1.17227E−11 A12−3.31780E−14 m 11 κ 11.00000 A4 −5.42096E−05 A6 −3.10136E−07 A8 1.12406E−09 A10 −6.77479E−11 A12 0.00000 m 19 κ 1.00000 A4 −9.95519E−06A6 −1.63819E−07 A8  7.91554E−09 A10 −7.12206E−11 A12 0.00000 m 24 κ1.00000 A4  6.12158E−05 A6  9.54377E−08 A8  7.65997E−09 A10 −1.66332E−10A12 0.00000 m 35 κ 1.00000 A4  4.40945E−05 A6  4.55406E−08 A8−1.64694E−10 A10 0.00000 A12 0.00000 [Various Data] Variablemagnification ratio 14.13 W T f 9.27 ~ 130.95 FNO 3.62 ~ 5.80 ω 42.35 ~3.34° Y 8.00 ~ 8.00 TL 107.68 ~ 161.55 W M T f 9.27006 35.10507130.95123 ω 42.35293 12.26813 3.33615 FNO 3.62 4.86 5.80 φ 9.50 9.509.50 d5 1.99992 27.74462 49.07741 d11 26.66183 8.84274 1.60231 d271.50002 3.35186 1.50007 d33 2.49955 19.42198 34.34914 BF 13.8495013.85022 13.85075 [Moving Amount of Focusing Lens Group upon Focusing] WM T shooting −0.0100 −0.0100 −0.0100 magnification photograohing1012.7397 3564.3738 13007.0879 distance moving 0.0448 0.0946 0.2525amount [Lens Group Data] ST f G1 1 72.95815 G2 6 −9.72184 G3 13 19.81920G4 28 −39.80048 G5 34 148.96616 [Vibration Reduction Coefficient] W M Tvibration reduction −1.25 −1.80 −2.16 coefficient [Values forConditional Expressions] (1) ff/(−fv) = 1.088 (2) (−fv)/f3 = 1.229 (3)(−fv)/f3A = 1.365 (4) ff/f3 = 1.337 (5) (−fv)/fm = 0.476 (6) ff/fm =0.518 (7) f1/fw = 7.870 (8) (−f4)/f5 = 0.267 (9) f5/fw = 16.070 (10) (d4t − d4w)/ft = 0.243

FIGS. 2A, 2B and 2C are graphs showing various aberrations upon focusingon an infinitely distant object in the wide-angle end state, in theintermediate focal length state and in the the telephoto end state ofthe variable magnification optical system according to the first exampleof the present application.

FIGS. 3A, 3B and 3C are graphs showing various aberrations upon focusing(shooting magnification—0.01 times) on the close object in thewide-angle end state, in the intermediate focal length state and intelephoto end state of the variable magnification optical systemaccording to the first example of the present application.

FIGS. 4A, 4B and 4C are graphs showing meridional transverse aberrationsat the time of conducting vibration reduction upon focusing on theinfinitely distant object in the wide-angle end state, in theintermediate focal length state and in the telephoto end state of thevariable magnification optical system according to the first example ofthe present application, more specifically, meridional transverseaberrations in the center of the image plane and an image height ±5.6 atthe time when the V lens group GV is moved 0.1 mm in a directionperpendicular to the optical axis.

For example, in the variable magnification optical system according tothe present example, since, in the wide-angle end state, the vibrationcoefficient is −1.25 and the focal length is 9.27 mm, with the V lensgroup GV being moved 0.1 mm from the optical axis, it is possible tocorrect a rotational shake of −0.77° of a plane of rotation includingthe optical axis.

In graphs showing various aberrations, FNO denotes an F number, NAdenotes a numerical aperture of light incident on the first lens groupG1, A denotes an incident angle of light, that is, a half angle of view(unit is “º”), and HO denotes an object height (unit is “mm”. d and gshow aberrations respectively at d-line (wavelength 587.6 nm) and atg-line (wavelength 435.8 nm). In the case where d or g is not written inthe graphs, the graphs show aberrations at d-line. In graphs showingastigmatism, a solid line represents a sagittal image plane and a brokenline represents a meridional image plane. Note that in graphs showingaberrations of a second example hereinafter described, the same symbolsare used.

From the graphs showing the various aberrations, it is understood thatthe variable magnification optical system according to the presentexample corrects the various aberrations over from the wide-angle endstate to the telephoto end state well thereby to have superb imageforming performance, further have superb image forming performance evenat the time of vibration reduction.

Second Embodiment

FIGS. 5A, 5B and 5C are sectional views showing a wide-angle end state,an intermediate focal length state and a telephoto end state of avariable magnification optical system according to a second examplewhich is common to the first to third embodiments of the presentapplication.

The variable magnification optical system according to the presentexample is composed of, in order from an object side: a first lens groupG1 having positive refractive power; a second lens group G2 havingnegative refractive power; a third lens group G3 having positiverefractive power; a fourth lens group G4 having negative refractivepower; and a fifth lens group G5 having positive refractive power whichis an R lens group.

The first lens group G1 consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L11 with a convexsurface facing the object side cemented with biconvex positive lens L12,and a positive meniscus lens L13 with a convex surface facing the objectside.

The second lens group G2 consists of, in order from the object side, anegative meniscus lens L21 with a convex surface facing the object sidewhich is a first lens, and a cemented lens constructed by a positivemeniscus lens L22 with a concave surface facing the object side which isa second lens cemented with a negative meniscus lens L23 with a concavesurface facing the object side which is a third lens. The negativemeniscus lens L21 is a compound type aspherical lens whose object sideglass surface is provided with a resin layer so as to be an asphericalshape. The negative meniscus lens L23 is a glass mold type asphericallens whose image side lens surface is made to be an aspherical shape.

The third lens group G3 is composed of, in order from the object side, a3A lens group G3A having positive refractive power, a V lens group GVhaving negative refractive power, an M lens group GM having positiverefractive power and an F lens group GF having positive refractivepower.

The 3A lens group G3A consists of, in order from the object side, apositive meniscus lens L31 with convex surface facing the object side,and a biconvex positive lens L32.

The V lens group GV consists of, in order from the object side, acemented lens constructed by a positive meniscus lens L33 with a concavesurface facing the object side cemented with a biconcave negative lensL34. The negative lens L34 is a glass mold type aspherical lens whoseimage side lens surface is made to be an aspherical shape.

The M lens group GM consists of, in order from the object side, acemented lens constructed by a biconvex positive lens L35 cemented witha negative meniscus lens L36 with concave surface facing the object sideand a negative meniscus lens L37 with a convex surface facing the objectside. The negative meniscus lens L37 is a glass mold type asphericallens whose image side lens surface is made to be an aspherical shape.

The F lens group GF consists of, in order from the object side, acemented lens constructed by a negative meniscus lens L38 with convexsurface facing the object side cemented with a biconvex positive lensL39.

An aperture stop S is disposed on the object side of the third lensgroup G3.

The fourth lens group G4 consists of, in order from the object side, abiconvex negative lens L41, a negative meniscus lens L42 with a concavesurface facing the object side and a biconvex positive lens L43.

The fifth lens group G5 consists of a positive meniscus lens L51 with aconcave surface facing the object side. The positive meniscus lens L51is a glass mold type aspherical lens whose image side lens surface ismade to be an aspherical shape.

With the above-mentioned construction, in the variable magnificationoptical system according to the present example, upon zooming from thewide-angle end state to the telephoto end state, the first to the fourthlens groups G1 to G4 are moved along the optical axis such that adistance between the first lens group G1 and the second lens group G2, adistance between the second lens group G2 and the third lens group G3, adistance between the third lens group G3 and the fourth lens group G4and a distance between the fourth lens group G4 and the fifth lens groupG5 are varied.

Specifically, the first lens group G1 to the fourth lens group G4 aremoved to the object side upon zooming. The position of the fifth lensgroup G5 is fixed in a direction of the optical axis upon zooming. Theaperture stop S is moved integrally with the third lens group G3 uponzooming.

Accordingly, upon zooming, the distance between the first lens group G1and the second lens group G2 increases, the distance between the secondlens group G2 and the third lens group G3 decreases, and the distancebetween the fourth lens group G4 and the fifth lens group G5 increases.Also, upon zooming, the distance between the third lens group G3 and thefourth lens group G4 increases from the wide-angle end state to theintermediate focal length state, and decreases from the intermediatefocal length state to the telephoto end state. A distance between the 3Alens group G3A and the V lens group GV of the third lens group G3 isconstant upon zooming.

Further, in the variable magnification optical system according to thepresent example, at the time of occurrence of a camera shake, the V lensgroup of the third lens group G3 is used as a vibration reduction lensgroup and moved so as to have a component in a direction perpendicularto the optical axis thereby to carry out vibration reduction.

Further, in the variable magnification optical system according to thepresent example, the F lens group of the third lens group G3 is used asa focusing lens group and moved along the optical axis to the objectside thereby to carry out focusing from an infinitely distant object toa close object.

In the following Table 2, various values associated with the variablemagnification optical system according to the present application arelisted.

TABLE 2 Second Example [Surface Data] m r d nd νd OP ∞  1 144.92271.6350 1.903660 31.27  2 46.4543 7.6180 1.497820 82.57  3 −280.82810.1000  4 45.6286 4.5089 1.804000 46.60  5 218.0774 d5  *6 500.00000.1000 1.553890 38.09  7 201.2901 1.0000 1.883000 40.66  8 8.9082 4.3024 9 −176.6896 4.5658 1.808090 22.74 10 −10.0014 1.0000 1.851350 40.10*11  −200.0095 d11 12 ∞ 0.9999 Aperture Stop S 13 23.8529 1.80951.589130 61.22 14 486.6979 0.1519 15 15.8304 2.0358 1.487490 70.31 16−215.8847 1.8715 17 −29.0336 2.6709 1.903660 31.27 18 −9.9974 1.00001.801390 45.46 *19  41.4658 1.8000 20 60.1509 3.0715 1.593190 67.90 21−10.4089 0.9998 2.000690 25.46 22 −16.9605 0.0998 23 489.2464 1.63861.851350 40.10 *24  70.3131 5.8990 25 15.2850 1.0000 2.001000 29.14 2610.6499 3.7035 1.618000 63.34 27 −78.8215 d27 28 −77.1108 1.00001.883000 40.66 29 19.2328 1.7995 30 −28.7053 1.0000 1.902650 35.73 31−58.4684 0.2013 32 27.7625 2.4973 1.698950 30.13 33 −42.9090 d33 34−45.3546 0.9996 1.583130 59.44 *35  −30.7592 BF I ∞ [Aspherical Data] m6 κ −8.74540 A4  2.25905E−05 A6  1.19617E−07 A8 −4.53045E−09 A10 3.58335E−11 A12 −1.06040E−13 m 11 κ 11.00000 A4 −5.72909E−05 A6−2.83675E−07 A8 −4.14714E−10 A10 −6.09625E−11 A12 0.00000 m 19 κ 1.00000A4 −9.91318E−06 A6 −1.59863E−07 A8  6.78573E−09 A10 −5.85391E−11 A120.00000 m 24 κ 1.00000 A4  4.62032E−05 A6  1.66004E−07 A8  1.04366E−09A10 −3.63478E−11 A12 0.00000 m 35 κ 1.00000 A4  4.27991E−05 A6 5.83932E−08 A8 −3.84157E−10 A10 0.00000 A12 0.00000 [Various Data]Variable magnification ratio 14.13 W T f 9.27 ~ 130.95 FNO 3.59 ~ 5.68 ω42.56 ~ 3.34° Y 8.00 ~ 8.00 TL 107.46 ~ 162.00 W M T f 9.27014 35.18344130.95207 ω 42.56336 12.24162 3.33601 FNO 3.59 4.79 5.68 φ 9.52 9.529.52 d5 2.00004 28.13283 49.85756 d11 26.52876 8.54977 1.50011 d271.49960 3.51536 1.49981 d33 2.49961 19.00799 34.21187 BF 13.8509013.85172 13.85176 [Moving Amount of Focusing Lens Group upon Focusing] WM T shooting −0.0100 −0.0100 −0.0100 magnification photograohing1012.6284 3571.8850 13006.4468 distance moving 0.0445 0.0953 0.2527amount [Lens Group Data] ST f G1 1 73.95013 G2 6 −9.75125 G3 13 19.75049G4 28 −40.13288 G5 34 159.88013 [Vibration Reduction Coefficient] W M Tvibration reduction −1.23 −1.77 −2.13 coefficient [Values forConditional Expressions (1) ff/(−fv) = 1.082 (2) (−fv)/f3 = 1.240 (3)(−fv)/f3A = 1.356 (4) ff/f3 = 1.342 (5) (−fv)/fm = 0.495 (6) ff/fm =0.536 (7) f1/fw = 7.977 (8) (−f4)/f5 = 0.251 (9) f5/fw = 17.247 (10) (d4t − d4w)/ft = 0.242

FIGS. 6A, 6B and 6C are graphs showing various aberrations upon focusingon an infinitely distant object in the wide-angle end state, in theintermediate focal length state and the telephoto end state of thevariable magnification optical system according to the second example ofthe present application.

FIGS. 7A, 7B and 7C are graphs showing various aberrations upon focusingon a close object (shooting magnification—0.01 times) in the wide-angleend state, in the intermediate focal length and in the telephoto endstate of the variable magnification optical system according to thesecond example of the present application.

FIGS. 8A, 8B and 8C are graphs showing meridional transverse aberrationsat the time of conducting vibration reduction upon focusing on theinfinitely distant object in the wide-angle end state, in theintermediate focal length state and in the telephoto end state of thevariable magnification optical system according to the second example ofthe present application, specifically, showing meridional transverseaberrations in the center of the image plane and an image height ±5.6 atthe time when the V lens group GV is moved 0.1 mm in a directionperpendicular to the optical axis.

For example, in the variable magnification optical system according tothe present example, since, in the wide-angle end state, the vibrationcoefficient is −1.23 and the focal length is 9.27 mm, with the V lensgroup GV being moved 0.1 mm from the optical axis, it is possible tocorrect a rotational shake of −0.77° of the plane of rotation includingthe optical axis.

From the graphs showing the various aberrations, it is understood thatthe variable magnification optical system according to the presentexample corrects well the various aberrations over from the wide-angleend state to the telephoto end state thereby to have superb imageforming performance, further have superb image forming performance evenat the time of conducting vibration reduction.

According to the above examples, it is possible to achieve the compactvariable magnification optical system with a high zoom ratio and highoptical performance. Also, high optical performance can be achieved uponfocusing and even when the lens group is moved so as to have thecomponent in the direction perpendicular to the optical axis. The aboveexamples are concrete examples of the invention of the presentapplication and the invention of the present application is not limitedthereto. Contents to be described below are adoptable in such a range asnot deteriorating optical performance of the variable magnificationoptical system according to the first to the third embodiments of thepresent application.

Although the five-lens-group configuration is adopted in the variablemagnification optical system according to the first to the thirdembodiments of the present application, the present application is notlimited thereto and can adopt an other-lens group configuration (forexample, a six-lens group configuration). Specifically, a lens or a lensgroup may be added on the most object side and on the most image side ofthe variable magnification optical system of the first to the thirdembodiments of the present application. Note that the lens group means aportion including at least one single lens separated by air spaces.

Further, in the variable magnification optical system according to thefirst to the third embodiment of the present application, in order toconduct focusing from the infinitely distant object to the close object,a portion of the lens group, a whole lens group or a plurality of lensgroups may be made as the focusing lens group and moved in the directionof the optical axis. Particularly, it is preferable to make at least aportion of the second lens group, at least a portion of the third lensgroup, at least a portion of the fourth lens group or at least portionof the fifth lens group to be the focusing lens group. Such a focusinglens group is adaptable to an autofocus and a motor for an autofocus,for example, drive by an ultrasonic motor.

Further, in the variable magnification optical system according to thefirst to the third embodiments of the present application, any lensgroup as a whole, or a portion of any lens group is made as thevibration reduction lens group and is moved so as to have a componentperpendicular to the optical axis, or rotationally moved, oscillated orswayed in a direction of a plane including the optical axis to carry outvibration reduction. In the variable magnification optical systemaccording to the first to the third embodiments of the presentapplication, it is preferable to make at least a portion of the thirdlens group or at least a portion of the fourth lens group to be thevibration reduction lens group.

Further, the lens surfaces constituting the variable magnificationoptical system according to the first to the third embodiments of thepresent application may be spherical surfaces, plane surfaces oraspherical surfaces. In the case where a lens surface is a sphericalsurface or a plane surface, lens processing and assembling adjustmentbecome easy, so that it is possible to prevent deterioration of opticalperformance due to errors of lens processing and assembling adjustment.So, this is preferable. Also, when the image plane is deviated,deterioration of image forming performance is small, so that it ispreferable. In the case where a lens surface is an aspherical surface,the aspherical surface may be an aspherical surface formed by means ofgrinding, a glass mold type aspherical surface formed by molding a glassinto an aspherical surface or a compound type aspherical surface formedby forming a resin on a surface of a glass so as to be an asphericalsurface shape. Also, a lens surface may be a diffractive opticalsurface, and a lens may be a graded-index type lens (GRIN Lens) or aplastic lens.

Further, in the variable magnification optical system according to thefirst to the third embodiments, it is preferable to dispose the aperturestop in the third lens group or in the vicinity of the third lens group.Also, the member as the aperture stop may not be provided and a lensframe may be used for that role.

Further, a lens surface of the lens constituting the variablemagnification optical system according to the first to the thirdembodiments of the present application may be formed with anantireflection coating having high transmittance in a wide wavelength.Thereby, flare and ghost images can be reduced, so that it is possibleto achieve high contrast and high optical performance.

Next, a camera equipped with the variable magnification optical systemaccording to the first to the third embodiments of the presentapplication will be explained with reference to FIG. 9.

FIG. 9 is a diagram showing a camera equipped with the variablemagnification optical system according to the first to third embodimentsof the present application.

A camera 1 as shown in FIG. 9 is a lens interchangeable type so-calledmirror-less camera equipped with the variable magnification opticalsystem according to the first example as an imaging lens 2.

In the camera 1, light emitted from an unillustrated object is collectedby the imaging lens 2 and passes through an unillustrated OLPF (Opticallow pass filter) to form an object image on an imaging plane of animaging part 3. Then, the object image is photo-electrically convertedby a photoelectric conversion element provided in the imaging part tocreate an image of the object. The created image is displayed on an EVF(Electronic view finder) 4. Thereby a photographer can observe theobject to be photographically taken via the EVF 4. Further, when thephotographer presses an unillustrated release button all the way down,the image photo-electrically converted by the imaging part 3 is storedin an unillustrated memory. In such a manner, the photographer can takea picture of the object with the camera 1.

Here, the variable magnification optical system according to the firstexample mounted on the camera 1 as the imaging lens 2 is compact and hasa high zoom ratio and high optical performance. Also, high opticalperformance can be achieved upon focusing and even when the lens groupis moved so as to have the component in the direction perpendicular tothe optical axis. Accordingly, it is possible to realize the compactcamera 1 with a high zoom ratio and high optical performance and realizehigh optical performance upon focusing and even when the lens group ismoved so as to have the component in the direction perpendicular to theoptical axis. In a camera equipped with the variable magnificationoptical system according to the second example as the imaging lens 2,the same effect can be obtained. Further, the same effect can beobtained even in the case where a single-lens reflex camera which isprovided with a quick return mirror and in which an object to bephotographically taken is observed via a finder optical system.

Finally, a method for manufacturing the variable magnification opticalsystem according to the first to the third embodiment will be explainedwith reference to FIGS. 10 to 12.

The method for manufacturing the variable magnification optical systemaccording to the first embodiment shown in FIG. 10, is a method formanufacturing a variable magnification optical system which comprises,in order from an object side: a first lens group having positiverefractive power; a second lens group having negative refractive power;and a third lens group having positive refractive power; the methodcomprising the following steps S11 to S13.

Step S11: Disposing in the variable magnification optical system a Vlens group having negative refractive power to be moved so as to havethe component in the direction perpendicular to the optical axis, and anF lens group having positive refractive power so as to be moved alongthe optical axis upon focusing from an infinitely distant object to aclose object.

Step S12: Disposing in a lens barrel, the first to the third lens group,in order from the object side, and disposing the V lens group and the Flens group such that the V lens group is positioned on a more objectside than the F lens group.

Step S13: Constructing such that, with providing a well-known movingmechanism in the lens barrel, upon zooming from a wide-angle end stateto a telephoto end state, a distance between the first lens group andthe second lens group and a distance between the second lens and thethird lens group are varied.

According to the method for manufacturing the variable magnificationoptical system according to the first embodiment of the presentapplication, it is possible to manufacture the compact variablemagnification optical system with a high zoom ratio and high opticalperformance, high optical performance being achieved upon focusing andeven when the lens group is moved in the direction perpendicular to theoptical axis.

A method for manufacturing the variable magnification optical systemaccording to the second embodiment shown in FIG. 11, is a method formanufacturing a variable magnification optical system which comprises,in order from an object side: a first lens group having positiverefractive power; a second lens group having negative refractive power;and a third lens group having positive refractive power; the methodcomprising the following steps S21 to S22.

Step S21: Constructing the third lens group to include an F lens grouphaving positive refractive power and being moved along the optical axisupon focusing from an infinitely distant object to a close object, anddisposing in a lens barrel the first to the third lens groups in orderfrom the object side.

Step S22: Constructing such that, with providing a well-known movingmechanism in the lens barrel, upon zooming from a wide-angle end stateto a telephoto end state, a distance between the first lens group andthe second lens group and a distance between the second lens and thethird lens group are varied.

According to the method for manufacturing the variable magnificationoptical system according to the second embodiment of the presentapplication, it is possible to manufacture the compact variablemagnification optical system with a high zoom ratio and high opticalperformance, high optical performance being achieved upon focusing andeven when the lens group is moved in the direction perpendicular to theoptical axis.

A method for manufacturing for the variable magnification optical systemaccording to the third embodiment shown in FIG. 12, is a method formanufacturing a variable magnification optical system which comprises,in order from an object side: a first lens group having positiverefractive power; a second lens group having negative refractive power;a third lens group having positive refractive power; a fourth lens grouphaving negative refractive power; and a fifth lens group having positiverefractive power; the method comprising the following steps S31 to S32.

Step S31: Constructing the fourth lens group and the fifth lens group tosatisfy the following conditional expression (8):0.170<(−f4)/f5<0.400  (8)

where f4 denotes a focal length of the fourth lens group, and f5 denotesa focal length of the fifth lens group; and

disposing the first to the fifth lens group in a lens barrel in orderfrom the object side.

Step S32: Constructing such that, with providing a well-known movingmechanism in the lens barrel, upon zooming from a wide-angle end stateto a telephoto end state, a distance between the first lens group andthe second lens group, a distance between the second lens and the thirdlens group, a distance between the third lens group and the fourth lensgroup and a distance between the fourth lens group and the fifth lensgroup are varied, the first lens group is moved along the optical axisand the position of the fifth lens group is fixed.

According to the method for manufacturing the variable magnificationoptical system according to the third embodiment of the presentapplication, it is possible to manufacture the compact variablemagnification optical system with a high zoom ratio and high opticalperformance.

What is claimed is:
 1. A variable magnification optical systemcomprising, in order from an object side, a first lens group havingpositive refractive power; a second lens group having negativerefractive power; and a third lens group having positive refractivepower; upon zooming from a wide-angle end state to a telephoto endstate, a distance between the first lens group and the second lens groupand a distance between the second lens group and the third lens groupbeing varied; and the third lens group including an F lens group havingpositive refractive power and being moved along an optical axis uponfocusing from an infinitely distant object to a close object.
 2. Thevariable magnification optical system according to claim 1, wherein thefollowing conditional expression is satisfied:0.320<ff/f3<5.200 where f3 denotes a focal length of the third lensgroup, and ff denotes a focal length of the F lens group.
 3. Thevariable magnification optical system according to claim 1, wherein theF lens group is a portion lens group of the third lens group.
 4. Thevariable magnification optical system according to claim 1, wherein theF lens group is disposed on a most image side of the third lens group.5. The variable magnification optical system according to claim 1,wherein a fourth lens group having negative refractive power is disposedon an image side of the third lens group and upon zooming from thewide-angle end state to the telephoto end state, a distance between thethird lens group and the fourth lens group is varied.
 6. The variablemagnification optical system according to claim 5, wherein a fifth lensgroup is disposed on an image side of the fourth lens group, and uponzooming from the wide-angle end state to the telephoto end state, adistance between the fourth lens group and the fifth lens group isvaried.
 7. The variable magnification optical system according to claim1, wherein an R lens group is disposed at an image side of the variablemagnification optical system and, upon zooming from the wide-angle endstate to the telephoto end state, a position of the R lens group isfixed.
 8. The variable magnification optical system according to claim1, wherein the following conditional expression is satisfied:5.500<f1/fw<9.000 where fw denotes a focal length of the variablemagnification optical system in the wide-angle end state, and f1 denotesa focal length of the first lens group.
 9. The variable magnificationoptical system according to claim 1, wherein the third lens groupincludes a V lens group having negative refractive power and beingmovable so as to have a movement component in a direction perpendicularto the optical axis.
 10. An optical apparatus equipped with the variablemagnification optical system according to claim
 1. 11. A method formanufacturing a variable magnification optical system, comprising:arranging, in order from the object side: a first lens group havingpositive refractive power; a second lens group having negativerefractive power; and a third lens group having positive refractivepower; constructing the third lens group to include a F lens grouphaving positive refractive power, the F lens group being disposed so asto move along an optical axis upon focusing from an infinitely distantobject to a close object; and constructing such that, upon zooming froma wide-angle end state to a telephoto end state, a distance between thefirst lens group and the second lens group and a distance between thesecond lens group and the third lens group are varied.
 12. The variablemagnification optical system according to claim 7, wherein the R lensgroup has positive refractive power.
 13. The variable magnificationoptical system according to claim 1, wherein an R lens group is disposedat an image side of the variable magnification optical system, and the Rlens group has an aspherical lens.
 14. The variable magnificationoptical system according to claim 1, including a V lens group havingnegative refractive power and being movable so as to have a movementcomponent in a direction perpendicular to the optical axis.